Took a quick look at the FSS MEDM screen and noticed that the RFPD DC value was fluctuating wildly.
Pulled up the filter for this channel and saw that the 2 Hz low-pass filter was not engaged and that
the gain value was set to 1.000.

The 2 Hz low pass filter is now engaged, as it should be, and the gain value was set to 0.150 which
gives readings consistent with those obtained with a digital multimeter plugged into the DC output of
the RFPD.